Transport of Solutes and Water

Transcription

1 Transport of Solutes and Water Across cell membranes 1. Simple and Facilitated diffusion. 2. Active transport. 3. Osmosis.

2 Simple diffusion Simple diffusion - the red particles are moving from an area of high concentration to areas of lower concentration Passive transport O 2 H 2 O

3 Simple diffusion

4 Ion diffusion depends on dual effects of concentration and electrical gradients Na + Concentration gradients give rise to the most elementary form of simple solute diffusion Electrical gradients often influence the diffusion of charged solutes at membranes

5 Ion diffusion depends on dual effects of concentration and electrical gradients

6 Ion diffusion Ion diffusion depends depends on on dual dual effects of concentration and and electrical electrical gradients gradients

7 Membrane permeable only for K + Semi permeable membrane

8 Ionic charge separation occurs only in the membrane vicinity

9 Diffusional concentration of a solute in a boundary layer next to an animal or cell

10 How to keep the intracellular fluid different in composition from the extra cellular fluid? H 2 O Cations: Positive H 2 O Anions: Negative

11 Channels in the membrane: Gated ion channels Simple diffusion Only in the direction of the electrochemical gradient Solutes move dissolved in the membrane or using channels. Oxygen Ions

12 Channels in the membrane: Gated ion channels Movement by electrochemical gradient Ion do not bind to the channel protein

13 Channels in the membrane: Gated ion channels Gated ion channels

14 Facilitated diffusion Solutes bind reversible to a transporter protein or carrier Carrier-mediated passive transport = facilitated diffusion Similar to simple diffusion, except particles move through a carrier mechanism instead of through a simple channel

15 Passive Transport Passive Transport Concentration gradient With With Energy necessary NO NO With Integral Protein PASSIVE Transport of molecules NO Simple Diffusion YES Facilitated Diffusion Examples > Small or Hydrophobic Substances (by simple diffusion) > Not-Small or Charged Substances (by facilitated diffusion) Facilitated diffusion

16 Facilitated diffusion Solutes bind reversible to a transporter protein or carrier Only in the direction of the electrochemical gradient

17 Cotransport (Symport) Solutes bind reversible to a transporter protein or carrier Cotransport (symport) involves more than one type of particle being transported by in the same direction at the same time by the same mechanism

18 Transport of molecules Active transport!!!!! Against the direction of the electrochemical gradient. Requires metabolic energy. Solutes bind reversible to transporter protein Active transport > Ions > Amino acids > Sugars

19 Transport of molecules across cell membranes Passive Transport Active Transport Concentration gradient With (Down) AGAINST (Up) Energy necessary NO YES Without Integral Protein YES (Simple Diffusion) NO With Integral Protein YES (Facilitated Diffusion) YES Examples > Small or Hydrophobic Substances (by simple diffusion) > Not-Small or Charged Substances (by facilitated diffusion) Cotransport, Proton Pump, Sodium-Potassium Pump 3 1 2

20 Transport of molecules How is Sodium transported? How is Glucose transported?

21 Figure 3.10 Summary of active and Active passive ion transport in a typical animal cell Na + -K + pump (countertransport ) 1. Against the direction of the electrochemical gradient. 2. Requires metabolic energy. 3. Solutes bind reversible to transporter protein

22 Primary active transport The transporter is an ATPase and energy comes DIRECTLY from ATP 1 The Na + K + -ATPase transduces ATP-bond energy into ion motive energy Phosphorilation-dephosphorilation changes AFFINITY of binding sites

23 Active transport Sodium potassium pump The sodium-potassium pump (Na+-K+ ATPase) is an example of countertransport in which two kinds of particles are transported at the same time in opposite directions by the same mechanism.

24 Primary active transport The transporter is an ATPase and energy comes DIRECTLY from ATP Phosphorilation-dephosphorilation changes AFFINITY of binding sites Two conformation states E1 selectively binds Na E2 selectively binds K

25 Facilitated diffusion and Active transport are carried- mediated transport Solutes bind reversible to a transporter protein or carrier Electrochemical gradient Metabolic energy requirement Transporter protein

26 Figure 3.1 Three focal examples in which transport occurs (Part 3) How do you keep glucose moving from the lumen of the intestine into the epithelium and into the blood?

27 Secondary active transport ATP is used to create an electrochemical gradient 1 2 Cotransporter and countertransport

28 Secondary active transport of glucose into an epithelial cell of small intestine (Part 1) countertransport

29 Figure Secondary 3.12 Secondary active transport active transport of glucose of glucose into an into epithelial an epithelial cell cell of small of small intestine (Part 2) 2)

30 Figure Secondary 3.12 Secondary active transport active transport of glucose of glucose into an into epithelial an epithelial cell cell of small of small intestine (Part 3) 3) Cotransporter

31 Figure 3.13 Two perspectives on epithelial active transport (Part 1) Secondary active transport of glucose into an epithelial cell of small intestine (Part 4)

32 Active ion uptake across epithelial cells of freshwater fish gills

33 How to keep the difference in composition between the fish blood plasma and the fresh water?

34 Cellular mechanism of ion pumping across epithelial cells of freshwater fish gills 1. Electrogenic proton pump 2. Na-K pump Two independent mechanisms countertransport protein HCO 3 electrochemical gradient

35 Transport mechanisms of in the kidney Co-transport of glucose Co-transport of K and 2Cl Na enters by a channel

36 Osmosis: is the passive transport of water across a membrane. Depends on the number of dissolved molecules per volume. Water moves from LOW to HIGH osmotic pressure. Water moved from Hyposmotic to Hiperosmotic.

37 Osmosis: is the passive transport of water across a membrane. Water moves from LOW to HIGH osmotic pressure. Water moves from Hyposmotic to Hiperosmotic. isosmotic LOW Hyposmotic Hyperosmotic LOW

38 Osmotic uptake of water by a freshwater animal

39 There is a NaCl gradient in the medullary interstitial fluid that surrounds the collecting ducts Production of concentrated urine

40 Aquaporin Nobel Price Medicine 2003 Peter Agre Johns Hopkins School of Medicine in Baltimore. Channel proteins transport water down a concentration gradient from an area of higher concentration to an area of lower concentration. In the case of water, the channel proteins are called aquaporins.

41 An electrochemical view of a typical animal cell

42 Active and passive ion transport in a typical animal cell

43 Exocytosis Exocytosis is a kind of bulk transport in which large amounts of material are moved out of a cell. Notice also that new membrane is added to the plasma membrane (from the secretion vesicle)

44 RECEPTOR-MEDIATED ENDOCYTOSIS: Endocytosis in which specific molecules become bound to specific receptors on the cell surface and subsequently enter the cytoplasm enclosed in vesicles.

45 Endocytosis Endocytosis is a kind of bulk transport where large amounts of material are brought into a cell. Notice the role of receptors in identifying what is "good to eat" and that membrane is removed from the plasma membrane.